theta.md                package:MASS                R Documentation

_E_s_t_i_m_a_t_e _t_h_e_t_a _o_f _t_h_e _N_e_g_a_t_i_v_e _B_i_n_o_m_i_a_l _b_y _D_e_v_i_a_n_c_e

_D_e_s_c_r_i_p_t_i_o_n:

     Given the estimated mean vector, estimate 'theta' of the Negative
     Binomial Distribution by equating the deviance to the residual
     degrees of freedom. Analogue of a moment estimator.

_U_s_a_g_e:

     theta.md(y, u, dfr, limit = 20, eps = .Machine$double.eps^0.25)

_A_r_g_u_m_e_n_t_s:

       y: Vector of observed values from the Negative Binomial. 

       u: Estimated mean vector. 

     dfr: Residual degrees of freedom (assuming 'theta' known). 

   limit: Limit on the number of iterations. 

     eps: Tolerance to determine convergence. 

_V_a_l_u_e:

     The required estimate of 'theta', as a scalar.

_S_e_e _A_l_s_o:

     'glm.nb', 'theta.ml', 'theta.mm'

_E_x_a_m_p_l_e_s:

     ## Don't run: theta <- theta.md(y, fitted(fm), dfr = 123)

